Acetolactate synthase
| Acetolactate synthase | ||
|---|---|---|
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| Ribbon model according to PDB 1n0h | ||
| Mass / length primary structure | 74937 Da , 677 amino acids | |
| Secondary to quaternary structure | Homodimer | |
| Cofactor | Thiamine pyrophosphate , Mg 2+ | |
| Identifier | ||
| Gene name (s) | ILV2 | |
| External IDs |
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| Enzyme classification | ||
| EC, category | 2.2.1.6 , transketolase | |
| Response type | Decarboxylation | |
| Substrate | Pyruvate | |
| Products | α-acetolactate , CO 2 | |
The acetolactate synthase (abbreviated as or AHAS) is an enzyme that in many pro- and eukaryotes in the formation of branched chain amino acids is involved in valine, leucine and isoleucine. The enzyme is found in plants and unicellular organisms. A homologous gene has been identified in humans that may be associated with CADASIL . This article shows the enzyme from baker's yeast, Saccharomyces cerevisiae .
Layout and function
The enzyme is made up of two subunits and contains thiamine pyrophosphate as a prosthetic group .
Acetolactate synthase catalyzes the first step in the synthesis of valine , leucine and isoleucine , three amino acids that are essential for humans, by splitting CO 2 from two molecules of pyruvate . In the process, α-acetolactate is formed, which forms the basis for the further synthetic route.
The enzyme can be inhibited by various herbicides ( HRAC class B ). The effect of sulfonylureas (e.g. chlorsulfuron ) and imidazolinones (e.g. imazaquin ) is based on this point of attack . Some plants are resistant due to natural or now also induced mutations in the corresponding gene, since the inhibition can already be ineffective when an amino acid is exchanged, but the enzyme does not have to lose its function.
In addition, some bacteria of the genera Enterobacter , Aeromonas , Bacillus and Serratia produce 2,3-butanediol as the end product in the mixed acid fermentation from pyruvate , the first step also being catalyzed by acetolactate synthase.
Individual evidence
- ↑ A. Joutel, A. Ducros, S. Alamowitch, C. Cruaud, V. Domenga, E. Maréchal, K. Vahedi, H. Chabriat, MG Bousser, E. Tournier-Lasserve: A human homolog of bacterial acetolactate synthase genes maps within the CADASIL critical region . In: Genomics . tape 38 , no. 2 , December 1, 1996, pp. 192-198 , doi : 10.1006 / geno.1996.0615 , PMID 8954801 .
- ^ Siew Siew Pang, Luke W. Guddat, Ronald G. Duggleby: Molecular basis of sulfonylurea herbicide inhibition of acetohydroxyacid synthase . In: The Journal of Biological Chemistry . tape 278 , no. 9 , February 28, 2003, p. 7639-7644 , doi : 10.1074 / jbc.M211648200 , PMID 12496246 .
- ^ Hans Walter Heldt, Birgit Piechulla: Plant biochemistry . Springer, Berlin, Heidelberg 2015, ISBN 978-3-662-44397-2 , pp. 281 , doi : 10.1007 / 978-3-662-44398-9_1 .
- ↑ David P. Clark, Nanette Jean Pazdernik: Molecular Biotechnology: Fundamentals and Applications . Spectrum, Akad. Verl, Heidelberg 2009, ISBN 978-3-8274-2128-9 .
- ^ Georg Fuchs, Hans Günter Schlegel, Thomas Eitinger (eds.): General microbiology . 9th, completely revised and exp. Edition. Thieme, Stuttgart, New York 2014, ISBN 978-3-13-444609-8 .